This invention is directed to an improved mixed flow grain dryer and more particularly a mixed-flow grain dryer having a vacuum cool heat recovery system.
Various methods of drying grain are well-known in the art. Cross-flow dryers provide airflow in a direction perpendicular to the flow of the grain. They utilize perforated screens to hold the grain into columns while allowing air to pass through. This results in uneven temperature distribution of grain in the column. A further development of the cross-flow design allows for recovering heat from grain as it is cooled in the column, dramatically increasing fuel efficiency. This process is known as vacuum-cooling. The perforated screens minimize the amount of particulate drawn out of the grain column so that the warmed air may be recycled into the dryer with minimal risk of fire.
Mixed-flow dryers utilize lower airflow, slower grain heating rates and give consistent air temperature and humidity to all the grain going through the dryer. Both of these things are beneficial to grain quality and drying efficiency. Because of the large airflow ducts in mixed-flow dryers, however, they must utilize pressure-cooling to keep particulate in the grain from entering the fan, heater, and drying plenum where a fire could start. With this design, air heated by the grain cooling process is exhausted to the atmosphere. Not only is this wasteful, but the process reduces the fuel efficiency of the grain dryer. Therefore, a need exists in the art for a dryer that addresses these problems.
An objective of the present invention is to provide a grain dryer that utilizes a mixed-flow drying chamber and recirculates air heated during a cross-flow cooling process.
Another objective of the present invention is to provide a grain dryer that increases fuel efficiency while maintaining optimal grain quality.
These and other objectives will be apparent to those skilled in the art based upon the following written description, drawings, and claims.